Orthostatic intolerance in chronic fatigue syndrome

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background</jats:title> <jats:p>Orthostatic intolerance (OI) is a significant problem for those with chronic fatigue syndrome (CFS). We aimed to characterize orthostatic intolerance in CFS and to study the effects of exercise on OI.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>CFS (n = 39) and control (n = 25) subjects had recumbent and standing symptoms assessed using the 20-point, anchored, ordinal Gracely Box Scale before and after submaximal exercise. The change in heart rate (ΔHR ≥ 30 bpm) identified Postural Orthostatic Tachycardia Syndrome (POTS) before and after exercise, and the transient, exercise-induced postural tachycardia Stress Test Activated Reversible Tachycardia (START) phenotype only after exercise.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>Dizziness and lightheadedness were found in 41% of recumbent CFS subjects and in 72% of standing CFS subjects. Orthostatic tachycardia did not account for OI symptoms in CFS. ROC analysis with a threshold ≥ 2/20 on the Gracely Box Scale stratified CFS subjects into three groups: No OI (symptoms < 2), Postural OI (only standing symptoms ≥ 2), and Persistent OI (recumbent and standing symptoms ≥ 2).</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Dizziness and Lightheadedness symptoms while recumbent are an underreported finding in CFS and should be measured when doing a clinical evaluation to diagnose orthostatic intolerance. POTS was found in 6 and START was found in 10 CFS subjects. Persistent OI had symptoms while recumbent and standing, highest symptom severity, and lability in symptoms after exercise.</jats:p> <jats:p><jats:italic>Trial registration</jats:italic> The trial was registered at the following: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://clinicaltrials.gov/ct2/show/NCT03567811">https://clinicaltrials.gov/ct2/show/NCT03567811</jats:ext-link></jats:p> </jats:sec>